page 1 4 Climate Change 101: climate science basics

Climate Change 101: climate science basics

Physicians may be hesitant to talk about climate change because they aren’t

experts in climate science. In this section, you will find basic information about

climate change — what it is, what causes it, and what we can do about it.

But you don’t need to be a climate scientist to talk about the risks climate change

poses to human health, or the health benefits of taking action on climate change.

When physicians have a patient with a complex or rare illness, they often seek

guidance from a sub-specialist with extensive training and education on that illness.

Climate scientists are like sub-specialists — they are trained to understand climate

patterns, and the sophisticated models that forecast those patterns in the future. If

you were to consult with 100 climate scientists, you would find that:

97% of climate scientists agree: • Climate change is happening now.

• It is being driven primarily by human activity.

• We can do something to reduce its impacts and progression.

What’s the difference between weather, climate, climate variability and climate change? • Weather is the temperature, humidity, precipitation, cloudiness and wind that we

experience in the atmosphere at a given time in a specific location.

• Climate is the average weather over a long time period (30 – 50 years) in aregion.

• Climate variability refers to natural variation in climate that occurs over monthsto decades. El Niño, which changes temperature, rain and wind patterns in manyregions over about 2 – 7 years, is a good example of natural climate variability,also called natural variability.

• Climate change is “a systematic change in the long-term state of the atmosphereover multiple decades or longer.”1

° Scientists use statistical tests to determine the probability that changes in

the climate are within the range of natural variability — similar to the statistical tests used in clinical trials to determine whether a positive response to treatment is likely to have occurred by chance. For example, there is a less than 1% chance that the warming of the atmosphere since 1950 could be the result of natural climate variability.

Carbon dioxide (CO2) is the greenhouse gas responsible for greatest amount of warming to date.

FAST FACT:

© 2016 Public Health Institute/Center for Climate Change and Health

page 2 4 Climate Change 101: climate science basics

What causes climate change?2 At its most basic, climate change is caused by a change in the earth’s energy balance

— how much of the energy from the sun that enters the earth (and its atmosphere)

is released back into space. The earth is gaining energy as we reduce the amount of

solar energy that is reflected out to space — just like people gain weight if there is

an imbalance between calories in and calories out.

Since the Industrial Revolution started over 200 years ago, human activities have

added very large quantities of greenhouse gases (GHG) into Earth’s atmosphere.

These GHG act like a greenhouse (or a blanket or car windshield) to trap the sun’s

energy and heat, rather than letting it reflect back into space. When the

concentration of GHG is too high, too much heat is trapped, and the earth’s

temperature rises outside the range of natural variability. There are many GHG,

each with a different ability to trap heat (known as its “global warming potential”)

and a different half-life in the atmosphere. GHG are sometimes called “climate

active pollutants” because most have additional effects, most notably on human

health.

Photo credit: Marinebio

Carbon dioxide (CO2) is the GHG responsible for greatest amount of warming to

date. CO2 accounted for 82% of all human-caused GHG emissions in the U.S. in

2013.3 The majority of CO2 is released from the incomplete combustion of fossil

fuels - coal, oil, and gas — used for electricity production, transportation and

industrial processes. Together, these three activities account for more than 80% of

the CO2 released into the atmosphere.

Other important GHG include methane, nitrous oxide, black carbon, and various

fluorinated gases. Although these gases are emitted in smaller quantities than CO2,

they trap more heat in the atmosphere than CO2 does. The ability to trap heat is

measured as Global Warming Potential (GWP). As the most common and abundant

greenhouse gas, CO2 has a GWP of 1, so all other GHG warming potentials are

compared to it. Fluorinated gases, for example, have GWPs thousands of times

greater than CO2, meaning that pound-for-pound, these gases have a much

stronger impact on climate change than CO2.

Together, electricity production, transportation and industrial processes account for more than 80% of the CO2 released into the atmosphere.

FAST FACT:

© 2016 Public Health Institute/Center for Climate Change and Health

page 3 4 Climate Change 101: climate science basics

Summary Table of Greenhouse Gas Emissions 4 5

Name

% of U.S.

GHG

Emissions

2013

Sources Lifetime in the Atmosphere Global Warming

Potential (GWP)

Carbon

Dioxide

(CO2)

82%

Electricity production,

transportation, numerous

industrial processes.

Approximately 50-200 years.

Poorly defined because CO2 is

not destroyed over time; it

moves among different parts

of the ocean–atmosphere–

land system.

1

Methane

(CH4) 10%

Livestock manure, food

decomposition; extraction,

distribution and use of natural

gas

12 years 25

Nitrous oxide

(N2O) 5% Vehicles, power plant emissions 115 years 298

Black carbon

(soot, PM) >1%

Diesel engines, wildfires

biomass in household cook

stoves (developing countries)

Days to weeks 3,200

Fluorinated

gases: PFCs,

HFCs, NF3,

SF6

>5%

No natural sources. These are

synthetic pollutants found in

coolants, aerosols, pesticides,

solvents, fire extinguishers.

Also used in the transmission

electricity.

PFCs: 2600 – 50,000 years HFCs: 1-270 years NF3: 740 years

SF6: 3200 years

PFCs: 7,000–12,000 HFCs: 12–14,000 NF3: 17,2000

SF6: 22,800

Why Short-Lived Climate Pollutants Matter The greenhouse gases with a high global warming potential but a short lifetime in

the atmosphere are called “short-lived climate pollutants” (SLCP). Key SLCP

include methane, black carbon, and the fluorinated gases. Because of the

combination of a short half-life and high GWP, the climate change impacts of the

SLCP are front-loaded — more of the impacts occur sooner, while the full weight of

impacts from CO2 will be felt later.

© 2016 Public Health Institute/Center for Climate Change and Health

page 4 4 Climate Change 101: climate science basics

We must transition to carbon-free transportation and energy systems, because

CO2 remains the greatest contributor to climate change. But reducing emissions of

short-lived climate pollutants may “buy time” while we make the transition.

Reducing global levels of SLCP significantly by 2030 will:6

• Reduce the global rate of sea level rise by 20% by 2050

• Cut global warming in half, or 0.6° C, by 2050 and by 1.4° C by 2100

• Prevent 2.4 million premature deaths globally each year

• Improve health, especially for disadvantaged communities

Many strategies to reduce SLCP also have immediate health benefits, such as:

• Reducing air pollution related hospitalizations

• Promotion of reduced meat consumption

• Stricter emissions standards, especially for diesel vehicles

• Cleaner household cook stoves in developing nations

Climate change is causing five critical global environmental changes:7 • Warming temperature of the earth’s surface and the oceans: The earth has

warmed at a rate of 0.13° C per decade since 1957, almost twice as fast as itsrate of warming during the previous century.

• Changes in the global water cycle (‘hydrologic’ cycle): Over the past centurythere have been distinct geographical changes in total annual precipitation, withsome areas experiencing severe and long-term drought and others experiencingincreased annual precipitation. Frequency and intensity of storms increases asthe atmosphere warms and is able to hold more water vapor.

• Declining glaciers and snowpack: Across the globe, nearly all glaciers aredecreasing in area, volume and mass. One billion people living in river watershedsfed by glaciers and snowmelt are thus impacted.

• Sea level rise: Warmer water expands, so as oceans warm the increased volumeof water is causing sea level rise. Melting glaciers and snowpack also contributeto rising seas.

• Ocean acidification: Oceans absorb about 25% of emitted CO2 from theatmosphere, leading to acidification of seawater.

These global changes result in what we experience as changes in our local weather

and climate:

• Greater variability, with “wetter wets”, “drier dries” and “hotter hots”

° More frequent and severe extreme heat events

° More severe droughts

° More intense precipitation, such as severe rains, winter storms and

hurricanes

• Higher average temperatures and longer frost-free seasons

• Longer wildfire seasons and worse wildfires

• Loss of snowpack and earlier spring runoff

• Recurrent coastal flooding with high tides and storm surges

Oceans absorb about 25% of emitted CO2 from the atmosphere, leading to acidification of seawater.

DID YOU

KNOW?

© 2016 Public Health Institute/Center for Climate Change and Health

page 5 4 Climate Change 101: climate science basics

• More frequent and severe floods due to intense precipitation and springsnowmelt

• Worsening air quality: Higher temperatures increase production of ozone (a keycontributor to smog) and pollen, as well as increasing the risk of wildfires.

• Longer pollen seasons and more pollen production

Photo credit: US Global Change Research Project Climate and Health Assessment

There is a less than 1% chance that the warming of the atmosphere since 1950 could be the result of natural climate variability.

In turn these regional and local climatic changes result in the environmental, social

and economic changes that are associated with human health impacts. These

impacts will be covered in greater detail throughout the guide, but the graphic

below provides an overview of the pathways linking climate change and human

health outcomes.

FAST FACT:

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Climate change in the U.S. Climate change will appear differently in different regions of the U.S., just as

different patients may experience the same illness differently, depending on pre-

existing health status, socioeconomic factors and environmental context. Below are

a few snapshots of measured changes associated with climate change in the U.S.8

For a more comprehensive view of how climate change is affecting the U.S. and

specific regions, see the National Climate Assessment. California-specific impacts

will be covered in greater detail throughout the Guide.

Climate change will appear differently in different regions of the U.S.

FAST FACT:

© 2016 Public Health Institute/Center for Climate Change and Health

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Mitigation strategies that offer feasible and cost-effective ways to reduce greenhouse gas emissions include the use of clean and renewable energy for electricity production; walking, biking, and using low-carbon or zero-emission vehicles; reducing meat consumption; less flying; changing agricultural practices; limiting deforestation; and planting trees.

There is a lot we can do about climate change. In general, climate solutions fall into two big buckets — “mitigation” and

“adaptation.” Increasingly, government and community organizations also talk

about measures to increase climate “resilience.” These concepts are not distinct,

and are all inter-related. From the Global Change Research Project:9

• Mitigation refers to “measures to reduce the amount and speed of future climatechange by reducing emissions of heat-trapping gases or removing carbon dioxidefrom the atmosphere.”

• Adaptation refers to measures taken to reduce the harmful impacts of climatechange or take advantage of any beneficial opportunities through “adjustments innatural or human systems.”

• Resilience means the “capability to anticipate, prepare for, respond to, andrecover from significant threats with minimum damage to social well-being, theeconomy, and the environment.”

Mitigation Mitigation is essential because scientists agree that the higher global temperatures

rise, the greater the adverse consequences of climate change. Also, if emissions are

unchecked, there is a greater danger of abrupt climate change or surpassing

“tipping points.” For example, collapse of the West Antarctic Ice Sheet could lead to

very rapid sea level rise, or melting of permafrost could lead to large releases of

methane that would further increase warming through a positive feedback loop.

Catastrophic climate change could surpass our capacity to adapt. For example, a

recent study suggests that heat levels in parts of the Middle East may exceed the

body’s survival threshold unless we reduce greenhouse gas emissions levels

quickly.10

There are many mitigation strategies that offer feasible and cost-effective ways to

reduce greenhouse gas emissions. These include the use of clean and renewable

energy for electricity production; walking, biking, and using low-carbon or zero-

emission vehicles; reducing meat consumption; less flying; changing agricultural

practices; limiting deforestation; and planting trees.

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Our Carbon Budget In 2015, nearly 200 nations agreed in Paris that the risks are significantly

reduced if we can keep global temperatures from rising more than 1.5° Celsius

above pre-industrial levels. Currently, average global temperatures are around

1°C higher than pre-industrial levels, and if greenhouse gas emissions continue

at the current rates (“business as usual”), the Earth’s temperature will rise

about 4° C by the end of the century. To stay below 1.5° rise requires that from

now forward, total global emissions cannot exceed 240 billion tons of carbon

into the Earth’s atmosphere. This is referred to as our “carbon budget.” 11 At

current emissions rates, this carbon budget will be used up within the next 6 to

11 years. Therefore, drastic action is needed to significantly reduce emissions

as soon as possible.

© 2016 Public Health Institute/Center for Climate Change and Health

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Adaptation Adaptation strategies are needed to reduce the harmful impacts of climate change

and allow communities to thrive in the face of climate change. The impacts of

climate change are already evident – in extreme weather, more explosive wildfires,

higher temperatures, and changes in the distribution of disease-carrying vectors.

Because GHG persist in the atmosphere for a long time, more serious climate

impacts would be experienced even if we halted all GHG emissions today.

Cool roofs, planting trees, and air conditioning are all effective adaptation

strategies to reduce the impacts of rising temperatures and more frequent heat

waves. Seawalls and restoration of wetlands are both strategies to address sea

level rise. Emergency preparedness planning that takes climate changes into

account is one way to adapt to the increased frequency of climate resilience: the

capacity to anticipate, plan for and reduce the dangers of the environmental and

social changes brought about by climate change, and to seize any opportunities

associated with these changes.12 For more on climate change resilience see Climate

Change and Health Equity.

Climate and Health Co-Benefits Although climate change is the greatest health challenge of our century, action to

address it has the potential for huge health benefits. Consideration of the health

and equity impacts of various mitigation and adaptation strategies can help

optimize the health benefits of climate action. For more information on the health

co-benefits of climate actions, see the following “Climate Action for Healthy People,

Healthy Places, Healthy Planet” briefs:

• Transportation, Climate Change and Health: Reducing vehicle miles traveledthrough walking, biking, and public transit increases physical activity, significantlyreduces chronic disease risks and reduces greenhouse gas emissions.

• Energy, Climate Change and Health: Switching from coal combustion to clean,safe, renewable energy is one of the most important things we can do for ourhealth and for the climate.

• Food & Agriculture, Climate Change and Health: Shifting to healthy diets andlocal, sustainable food and agriculture systems, offers significant health, climate,and environmental benefits.

• Urban Greening & Green Infrastructure, Climate Change and Health: Urbangreening reduces the risk of heat illness and flooding, lowers energy costs, andsupports health. Green spaces provide places to be physically active and treessequester CO2, improve air quality, capture rainwater and replenishgroundwater.

The impacts of climate change are already evident — in extreme weather, more explosive wildfires, higher temperatures, and changes in the distribution of disease-carrying vectors.

The carbon budget includes the remaining amount of all GHG that can be emitted to keep the earth’s

temperature below the target of 1.5° Celsius. In order to provide a single, standardized measurement,

the global warming potentials of all GHG are converted to their CO2 equivalent and this figure (240

billion tons) is the carbon budget.

FAST FACT:

© 2016 Public Health Institute/Center for Climate Change and Health

page 9 4 Climate Change 101: climate science basics

Because greenhouse gasses (GHG) persist in the atmosphere for a long time, more serious climate impacts would be experienced even if we halted all GHG emissions today.

For More Information • Intergovernmental Panel on Climate Change Fifth Assessment Report

https://www.ipcc.ch/report/ar5/syr/

• U.S. Global Change Research Project National Climate Assessmenthttp://nca2014.globalchange.gov

• U.S. Environmental Protection Agency Climate Change sitehttps://www3.epa.gov/climatechange/

• Climate Change in California

° Our Changing Climate 2012: Summary report from the Third Assessment

of Climate Change in California http://www.energy.ca.gov/2012publications/CEC-500-2012-007/CEC-500-2012-007.pdf

° Cal Adapt: Web-based tool allowing users to identify climate change risks

throughout the state http://cal-adapt.org

° California Climate Change: Official State of California site with resources

on statewide climate change and initiatives to reduce greenhouse gas emissions http://climatechange.ca.gov

Page 1 photo: H. Raab / flickr.com; page 2 photo: Bill Dickinson/flickr.com; page 3 photo: Tam Thi L C/ flickr.com; page 4 photo: NPS; page 8 photo: Penn State; page 9 photo: NASA/Kathryn Hansen; page 10: Lotus R/flickr.com.

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Citations 1

2

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4

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7

8

9

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Uejio, C.K., Tamerius, J.D., Wertz, K. & Konchar, K.M. (2015). Primer on climate science. In G Luber & J Lemery

(Eds.), Global Climate Change and Human Health (p. 5), San Francisco, CA: Jossey-Bass.

United States Environmental Protection Agency. Climate Change: Basic Information. Available at

https://www3.epa.gov/climatechange/basics/

United States Environmental Protection Agency (2016). Inventory of US greenhouse gas emissions and sinks:

1990-2014 (DRAFT). Available at https://www3.epa.gov/climatechange/ghgemissions/gases.html

Ibid.

California Environmental Protection Agency Air Resources Board. Proposed Short-Live Climate Pollutants

Reduction Strategy. April 2016. Available at

http://www.arb.ca.gov/cc/shortlived/meetings/04112016/proposedstrategy.pdf

Climate and Clean Air Coalition (2014). Time to act to reduce short-lived climate pollutants. Available at

http://www.ccacoalition.org/en/resources/time-act-brochure

Uejio, C.K., Tamerius, J.D., Wertz, K. & Konchar, K.M. (2015). Primer on climate science. In G Luber & J Lemery

(Eds.), Global Climate Change and Human Health (pp. 12-18), San Francisco, CA: Jossey-Bass.

US Global Change Research Project (2014). National Climate Assessment: Climate Change Impacts in the United

States. Washington, D.C. Available at http://nca2014.globalchange.gov

USGCRP, 2016: Appendix 5: Glossary and Acronyms. The Impacts of Climate Change on Human Health in the

United States: A Scientific Assessment. U.S. Global Change Research Program, Washington, DC, 307–312.

Pal, J. & Eltahir, E. (2016). Future temperature in southwest Asia projected to exceed threshold for human

adaptability. Nature Climate Change, 6:197-200. Available at

http://www.nature.com/nclimate/journal/v6/n2/full/nclimate2833.html

IPCC, 2014: Climate Change 2014: Synthesis Report. Contribution of Working Groups I, II and III to the Fifth

Assessment Report of the Intergovernmental Panel on Climate Change [Core Writing Team, R.K. Pachauri and L.A.

Meyer (eds.)]. IPCC, Geneva, Switzerland, 151 pp.

Island Press & The Kresge Foundation. (No Date). Bounce forward, urban resilience in the era of climate change.

Island Press. http://kresge.org/sites/default/files/Bounce-Forward-Urban-Resilience-in-Era-of-Climate-

Change-2015.pdf

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